Plastic Hinge Model for Performance-based Design of U-shaped Composite Beams

Although U-shaped composite beams have been widely used in the field due to the optimized sectional configuration and excellent constructability, no analysis model dedicated to U-shaped composite beams is available in design codes and guidelines. In the present study, based on failure mechanisms of U-shaped composite beams, a simplified plastic hinge model is proposed and its moment-rotation relationship is defined including strength-degradation for performance-based design. Various flexural failure modes including the concrete crushing, bar fracture, steel fracture, and steel buckling were considered for various types of U-shaped composite beams (conventional U-shaped steel, welded U-shaped steel, and bolt-connected U-shaped steel sections). For verification, the proposed plastic hinge model was compared with existing test results, and the comparison showed that the predictions by the proposed model matched well with the test results, including deformation-capacity. A parametric study was also performed, and the parametric study results can give an insight to the design of U-shaped composite beams.